The present invention relates to a method and apparatus for processing vegatable foodstuffs, and more particularly to improvements in a method and apparatus for comminuting corn, wheat, banana peels or other types of vegetable foodstuffs which are to be consumed by humans and/or animals. Still more particularly, the invention relates to improvements in a method and apparatus for comminuting soft vegetable foodstuffs.
Many industrially processed foodstuffs of vegetable origin must be converted into a readily flowable pulverulent or similar state prior to final processing. Thus, wheat, rye and other types of grains must be treated in a mill to be converted into flour or farina prior to baking, prior to making of macaroni or analogous foodstuffs, or prior to direct sale to consumers. The making of flour for bread and/or other bakery products involves an intensive drying of grains, slight wetting and subsequent comminution in one or more passes of a flour mill. Also, many vegetable foodstuffs which are being prepared for consumption by animals are introduced (in dried condition) into a crushing mill to be comminuted to a desired degree of fineness. The thus comminuted material is thereupon compacted to form pellets. In each instance, the vegetables must be dried prior to comminution, i.e., freshly harvested vegetables are dried prior to introduction into a mill, even if the actual comminution must be preceded by a slight or pronounced increase of moisture content. Thus, at least the majority of vegetable foodstuffs must become hard (as a result of drying) before they are ready to be comminuted in a flour mill or the like.
Pronounced drying of certain types of vegetable foodstuffs prior to comminution and conversion into shapes which are expected by the consumers presents many problems. Thus, the taste, the behavior during baking or cooking, the color and/or certain other characteristics of many types of flours are less than satisfactory as a direct or indirect result of drying prior to conversion into a pulverulent or like state. Moreover, satisfactory drying of many types of vegetable foodstuffs prior to comminution takes up relatively long periods of time or such drying must be promoted by resorting to bulky, complex and expensive drying units which contribute excessively to the cost of the ultimate product. Still further, traditional mills which are used for the making of flour, farina and analogous pulverulent substances are satisfactory for comminution of cereal grains or the like but are totally unsuited for comminution of many other types of vegetables. For example, a flour mill cannot be used for conversion of freshly harvested vegetables into flour or farina, especially if the freshly harvested foodstuffs contain a high percentage of moisture. Water and other liquids squeezed out of the freshly harvested foodstuffs would immediately contaminate a flour mill and would prevent orderly evacuation of comminuted material.
Attempts to convert freshly harvested vegetables with a high moisture content into a pulverulent or like state by resorting to conventional paste mills or dough mixers have met with little success. In fact, the conversion of raw vegetables into a paste merely aggrevates the problems which arise in connection with drying before the paste can be reduced into a pulverulent or like state. Thus, a paste mill or an analogous machine can be used solely for the making of vegetable pastes; however, its use in conversion of fresh or raw vegetables into flour or farina merely contributes to the overall cost and prolongs the conversion of raw materials into a mass of flour-like consistency.
The drying of grains presents additional problems due to the fact that such foodstuffs comprise several layers, especially outer layers, which prevent rapid expulsion of moisture from the interior of the grain. Therefore, the drying of grains prior to comminution in a flour mill or the like invariably involves prolonged drying by air to expensive forced drying in specially designed ovens. It is not desirable to grind prior to complete or sufficient drying because the preliminary grinding must be followed by extensive drying prior to renewed grinding for the purpose of obtaining flour, farina or a substance of similar consistency. In accordance with certain presently known proposals, freshly harvested or partially dried grains are treated to form a pulpy or dough-like mass, and such mass is mixed with dry flour or farina prior to further comminution. The admixture of flour or farine to dough is necessary in order to enable a conventional mill to treat such substances for the purpose of making flour or the like. The just described recirculation of substantial quantities of flour or farine through a mill (together with a mass of pasty or like consistency) contributes significantly to the bulk and energy requirements of the apparatus.